The families of two women claiming to be Nelson Mandela's secret daughters have contacted the executors of his estate in a bid to win legal acknowledgement of their parentage.

The team looking after Mandela's estate following his death in December has received a legal letter from Onica Mothoa and relatives of Mpho Pule, who died in 2009, asking for their alleged links to the late civil rights icon to be made official.

However, Michael Katz, a lawyer for the executors, has revealed the claimants are not seeking a share of Mandela's inheritance, which will be divided out between his widow and descendants.

Katz says of the legal bid, "They made the claim that they are descendants of Madiba (Mandela). They indicated that this wasn't a monetary claim."

Mothoa has told South Africa's The Star newspaper she wants a DNA test to prove Mandela was her father and insists her claim is not about money: "I know the Mandela family have always believed that I was being opportunistic because I wanted a share in the inheritance. That's not true. I just want them to acknowledge that Mandela is my father. No amount of millions can buy the identity of a person. It is very important even for my children, as well as my grandchildren, to know who they are."

Mandela is said to have fathered six children during his lifetime and he left a fortune of around $4 million following his death.